Journal of Asthma, 35(3), 291-296 (1 998)

Prevalence of Bronchial Asthma in Schoolchildren in Delhi

Sunil K. Chhabra: Chandra K. Gupta? Pragti Chhabra? and Sanjay Rajpall

Departments of ‘Cardiorespiratory Physiology and Bios ta t is t ics

Vallabhbhai Patel Chest lnstitute 3Departrnent of Preventive and Social Medicine

University College of Medical Sciences Delhi, lndia

Key words: Bronchial asthma; Epidemiology; Prevalence

ABSTRACT

There is a paucity of information on the prevalence of asthma in children in India. Some evidence suggests that asthma i s less common in developing than in the developed countries. The present study was carried out to estimate its current magnitude in children in Delhi. The questionnaire-based study was car- ried out in two randomly selected schools in Delhi. All the children were eli- gible. The age range was 4-1 7 years. The questionnaires were distributed to all the children present ( n = 2867) to be answered by either parent. The key questions were related to complaints of recurrent wheezing in the past, in the last 1 year, and also wheezing exclusively induced by exercise or colds. In all, 2609 questionnaires were completed and returned (response rate 91 %). There was a slight excess of males (54%). The prevalence of current asthma was 11.6% and past asthma was reported by 4.1 o/o of children, giving a cumula- tive prevalence of 15.7%. Exclusive exercise-induced asthma was 2.8% and that associated with colds, 2.3%. The current prevalence of all wheezing was

Address correspondence to: S. K. Chhabra, M.D., E-67, South Extension Part 1, New Delhi 110 049, India. Fax: 091-011- 725-7471.

291

Copyright 0 1998 by Marcel Dekker, Inc.

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.

292 Chhabra et al.

thus 16.7% and cumulative prevalence was 20.8%. While there was no sex- related difference in prevalence, wheezers were the highest in the 9-1 3 year age group. A significant association was found between the prevalence of wheezing and a family history of asthma (odds ratio 3.65) and presence of smokers in the family (odds ratio 1.62). When both the above factors com- bined, the odds ratio for risk of asthma was 4.58. There was no significant association with any economic class. Only 1 1 O/O of asthmatics had been labeled so by their physicians. The prevalence of bronchial asthma and wheez- ing in children in Delhi is quite high and comparable to that reported from sev- eral developed countries. A positive family history of asthma and presence of smokers in the family emerged as significant risk factors.

INTRODUCTION

Bronchial asthma is the commonest chronic respiratory disease of children. Its epidemiol- ogy has been studied in several countries but uncertainty persists about its precise magni- tude in different parts of the world. Some evi- dence exists that bronchial asthma is less common in developing countries (1-6), the prevalence rates ranging from 0.2 to 5.1%, whereas in developed countries rates up to 28% have been reported (7-20). Method- ological differences among the surveys may partly explain this wide range but variation in the distribution of risk factors and population differences may also be important. A uniform approach is yet to be evolved to measure the prevalence of asthma.

Very limited data are available on the preva- lence of asthma in India. A study carried out more than three decades ago in Patna in Eastern India by Vishwanathan (1) estimated current asthma to be 0.20/0. Since then, there has been no large-scale study. There is no information about the current scenario in India. The present study was carried out to determine the current mag- nitude of the problem.

MATERIALS AND METHODS

The study was carried out in two Delhi schools selected randomly. The total popula- tion of the two schools was 2955. A specially designed and pretested questionnaire was dis- tributed to those present in every class of the

schools. In all, 2867 children received the ques- tionnaires. The questionnaire was made up of three parts. Part A recorded information about educational status and income of the parents and the family size. Part B had questions designed to uncover symptoms suggestive of asthma. Part C had questions related to family history of asthma and other allergic disorders, smoking in the family, and the fuel used at home. The questionnaires were taken home by the children to be answered by either parent and returned within 2 days.

The key questions asked in Part B of the questionnaire were as follows: ( a ) Has your child ever suffered repeatedly in the past (more than 1 year ago) with cough and diffi- culty in breathing with wheezing sound?; (b) Did he/she get such symptoms at anytime during the last 1 year?; (c) Does your child get breathless with wheezing on running or playing?; (d ) Does your child get a breathing problem with wheezing after he/she catches a cold?; (e) Has your child ever been diag- nosed to have asthma? In addition, the par- ents were asked to name the drugs taken by the child if he/she ever had the above com- plaints.

,4ccording to the responses to the questions, the children were classified into four categories as follows: ( a ) Current asthmatics: history of recurrent wheezing during the past 1 year, or past history of recurrent wheezing and current history of exercise- or cold-induced wheezing, or current history of exercise- and cold- induced wheezing; (b) Probable asthmatics: his- tory of either exercise-induced or cold-induced

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.

Bronchial Asthma in Delhi 293

wheezing; (c) Past asthmatics: history of recur- rent wheezing in the past but no symptoms during the last 1 year and no current history of exercise- or cold-induced wheezing; and (12) Nonastknratics: those with a negative response to all the above questions. The sum of current and past asthmatics gave the cumulative prevalence, and the sum of current and prob- able asthmatics gave the prevalence of total wheezing.

The data were analyzed on SPSS 6.0 for Windows 3.1 software. Chi-squared test was applied to test the significance of association of prevalence with risk factors. Odds ratios (OR) with 95% confidence limits were calculated for risk factors having a significant association with prevalence. The significance of associa- tion of prevalence with these risk factors was tested at the CI = 0.05 level.

RESULTS

In all, 2609 out of 2867 who received the questionnaire responded. The response rate was 91%. The age and sex distribution is shown in Table 1. There was a slight excess of males. The total number of males was 1401 (53.7%) and females, 1208 (46.3%).

The distribution of children into the four diagnostic categories is shown in Table 2. The current asthmatics constituted 11.6% of the subjects and past asthmatics were 4.1%. The cumulative prevalence of asthma was 15.7%. Probable asthmatics constituted another 5.1% out of which 2.8% had only exercise-induced wheezing and 2.3% had only cold-induced wheezing. The current prevalence of all

Table 1. Age and Sex Distribution of Children

AGE (YEARS) MALES FEMALES

4-8 453 (32.3%)' 363 (30.0"/;,) 9-1 3 594 (42.4%) 552 (45.7%) 14-1 7 354 (25.3%) 293 (24.3%) Total 1401 (1 00%) 1208 (1 00%)

"Figures in parentheses are column percentages

wheezing (current plus probable asthmatics) was thus 16.7%. The remaining 79.1% were classified as nonasthmatics. The sex ratios in each of the categories of subjects were not significantly different (x2 = 2.76, p > 0.05). The prevalence of current, past, and probable asthma had a significant association with age (x2 = 14.27, p < 0.01), being greater in the younger ages. Although current and proba- ble asthma was the highest in the age group 9-13 years, the proportion of past asthmat- ics was the highest in the 4-8 year age group. The data are presented in Table 3.

The association of prevalence of current and probable asthma with economic status, family history of asthma, and smoking in the family is given in Table 4. According to the per capita income, the subjects were divided into three categories. No significant association was found with per capita income (x2 = 5.413, p > 0.05). A significant association was seen between prevalence of wheezing with the presence of smokers in the family (x2 = 15.90, p < 0.01; OR 1.62,95% confidence interval [CI] 1.28-2.05) and with a positive family history of asthma (x2 = 106.1, p < 0.01; OR 3.65,95% CI 2.82-4.73). When both the risk factors were

Table 2. Distribution of Children in the Four Diagnostic Categories

CATEGORY TOTAL MALES FEMALES

Current asthmatics 303 (1 1 .6"/0)" 1 68 (1 2 .O%) 135 (1 1 .2%) Past asthmatics 107 (4.1 %) 63 (4.5%) 44 (3.6%) Probable asthmatics 133 (5.1%) 75 (5.4%) 58 (4.8%)

Exercise-i nduced 59 (2.3%) 32 (2.3%) 27 (2.2%) Cold-induced 74 (2.8%) 43 (3.1%) 31 (2.6%)

Nonasthmatics 2066 (79.2%) 1095 (78.2%) 971 (80.4"%) Total 2609 (1 00%) 1401 (1 00%) 1208 (1 00%)

"Figures in parentheses are column percentages.

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.

294 Chhabra et al.

Table 3. Distribution of Children in Various Asthma Categories

AGE GROUP (YEARS) CURRENT ASTHMATICS PAST ASTHMATICS PROBABLE ASTHMATICS

4-8 9-1 3 14-1 7 Total

100 (33.0'/0)~ 52 (48.6%) 136 (44.9%) 31 (29.0%) 67 (22.1%) 24 122.4%)

303 (100%) 107 (1 OOo/o)

37 (27.8%) 60 (45.1 %) 36 (27.1%)

133 (1 OOo/o)

"Figures in parentheses are column percentages.

present, the odds for the occurrence were greatly increased (OR 4.58,95% CI 2.88-7.29). An overwhelming majority (96.2%) of house- holds used liquefied petroleum gas cylinders as domestic fuel and the remaining few used kerosene, coal, or wood. Therefore, role of domestic fuel in the causation of asthma could not be evaluated statistically.

Only 11% of the current asthmatics had been labeled as asthmatics by their physi- cians. The remaining 89% had not been diag- nosed as having asthma. Only 23.2% of the current asthmatics has taken antiasthma drugs. The remaining 76.8% had not taken these drugs or were not aware of the drugs they had taken.

DISCUSSION

Although clinical recognition of asthma is based on a cluster of symptoms (wheeze, breathlessness, and cough), variable or

reversible airflow obstruction and/or airway hyperresponsiveness are regarded as essential objective evidence. However, reversibility of obstruction may not always be demonstrable and the somewhat poor predictive value of air- way hyperresponsiveness because of its pres- ence in persons without asthma make these tools impractical for use in epidemiological studies (11,17,19). The most widely used and reliable method of measuring prevalence of asthma in a population remains a properly val- idated questionnaire.

A review of several studies carried out in United States (7-9), United Kingdom (10-12), Canada (13), Australia (14-16), New Zealand (171, and Scandinavian countries (18-20) revealed a wide range of reported figures for prevalence of asthma-from 1.6 to 28%. In the national survey in the United States (9), the cumulative prevalence of physician-diag- nosed asthma and/or recurrent wheezing was observed to be 9.5% and current preva- lence was 6.7%. In a national study in the

Table 4. Association of Wheezing with Risk Factors

CATEGORIES CHILDREN WITH CHILDREN WITHOUT RISK FACTOR OF RISK FACTOR WHEEZl NC WHEEZING

Per capita >Rs 100

<Rs 500

Family history Positive of asthma** Negative

Smoking in Yes the family*** No

monthly income* RS 500-1 000 195 165 65

119 291

118 313

1029 84 7 239

2 02 1803

404 1733

*x2 = 5.41 3 , p > 0.05; **x2 = 106.1, p < 0.0001; odds ratio 3.65, 95% CI 2.82-4.73; ***x2 = 15.90, p < 0.0001; odds ratio

1 US$ = RS 40. 1.62, 95% CI 1.28-2.05.

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.

Bronchial Asthma in Delhi 295

United Kingdom, Peckham and Butler (10) reported a physician-diagnosed cumulative asthma of 3.5% and identified a further 8.8% children as having wheezy bronchitis. In a more recent study from Nottingham, UK (12), 11.5% children had current wheezing and 5.9% had been diagnosed as asthmatics. Cumulative prevalence of wheezing was 17.5%. In a study carried out in New Zealand (17), 27.1% had a history of recurrent wheez- ing at some time, out of which 18.1% had clinically significant asthma, 14.4% being cur- rent. From Sweden, Holmgren et al. (20) reported the current prevalence of physician- diagnosed asthma as 2.4%, and from Oslo, Norway (18), a current prevalence of physi- cian-diagnosed asthma of 1.6% was reported with wheezing noted in 8.6% of children. In South Australia (16), the overall cumulative prevalence rate for asthma and/or wheezing was found to be 23-27% in two communities. The prevalence rates reported from develop- ing countries (1-6) have generally been lower than those reported from the Western nations. These have varied from 0.2 to 5%. While there may be true population differ- ences and variations in risk factors may con- tribute, a major explanation for this wide range lies in the methodologies adopted. Although some studies have considered any wheezing to represent asthma (11,16,17), oth- ers have classified it separately from asthma (10,12,18). Some have excluded subjects with colds-associated wheezing (9). Still others have reported a physician-diagnosed asthma separately (10,12,20). This lack of consensus makes international comparisons of preva- lence difficult, if not impossible.

The only reported study (1) from India was carried out by Vishwanathan in Patna in the eastern part of India and reported a current asthma prevalence of 0.2% in children up to 9 years of age. Asthma was not defined clearly. Our estimates are much higher. However, because of methodological differences, a strict comparison cannot be made between the two studies from India.

Our prevalence rates agree well with those observed in several developed countries (11,12,16,17). Such high figures have been observed when asthma has been defined to

include all subjects with wheezing, including that induced by colds or exercise. It has been suggested that all wheezy children should be considered as asthmatics (11). This is a clini- cally sound argument and was substantiated by the good response in such subjects to spe- cific antiasthma treatment (11). Exercise- induced asthma is a well-recognized entity and Williams and McNicol (21) have shown that colds-associated wheezing is the same dis- ease as asthma.

Although a higher prevalence has been reported in boys (10,18,20), we did not find any sex-related differences at any age. Similarly, Dodge and Burrows (7) did not find any difference between sexes in children. The higher prevalence in boys was found only until the age of 12 years by Skarpaas and Gulsvik (18) and 4 years by Holmgren et al. (20). The reason for this disagreement is not clear. A possibility of a diagnostic bias in favor of boys resulting in the use of a label of asthma needs to be considered because sex-related dif- ference has been found to be more marked for asthma than for wheezing (10,lS). Studies of familial aggregation (22), twins (23), and genetic markers (24) have strongly suggested the probability that predisposition to asthma has a genetic basis. Our results show that with a family history, asthma was 3.65 times more likely to occur compared to households with- out such history.

Evidence that involuntary smoking is associated with development of asthma is conflicting. Some workers have observed an increased risk of developing asthma in asso- ciation with maternal smoking (25,26), but others have not corroborated this. In the pre- sent study, we found a significantly higher prevalence of asthma in children in house- holds with smokers, the odds being 1.62 times compared to households without smokers. There has been no consistent reported association between asthma and socioeconomic class. We also did not observe any such association.

In conclusion, the current prevalence of all wheezing, including exercise-induced and colds-associated, was found to be 15.7% in children in Delhi. A positive family history of asthma and involuntary smoking emerged as

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.

296 Chhabra et al.

significant risk factors for the occurrence of asthma.

ACKNOWLEDGMENT

This study was supported by a grant from the Indian Council of Medical Research.

REFERENCES

1. Vishwanathan R, Prasad M, Thakur AK, et al: Epidemiology of asthma in an urban population. A random morbidity survey. ] lndiaii Mcd Assor 46:480 (1966).

2. Ozkaragoz K, Cakin F: Atopic children in Turkey. A n n Allergy 2713 (1969).

3. Asch AJ, Rabin DL, Hurwitz A, Medalie JM: Bronchial asthma in an Israeli community. Isrnel ] Med Sci 9104 (1973).

4. Bangham CRM, Hope RA: Exercise-induced asthma in Nepalese children. Clin Allcrgy I1 :273 (1981).

5. Woolcock AJ, Konthen PG, Sedgwick C: Bronchial reactivity of schoolchildren in an Indonesian village. Bid1 IUAT 57266 (1982).

6. Hseih KH, Shen JJ: Prevalence of childhood asthma in Taipei, Taiwan and other Asian pacific countries. J Astliiria 25:73 (1988).

7. Dodge RR, Burrows 8. The prevalence and incidence of asthma and asthma-like symptoms in a general population sample. Awi Rev Rrspir Dis Z22:567 (1980).

8. Mak H, Johnston P, Abbey H, Talamo RC: Prevalence of asthma and health service utilization of asthmatic children in an inner city. ] AIkrgy Clin Irninttnoi 70367 (1982).

9. Gergen PJ, Mullally DI, Evans R National survey of prevalence of asthma among children in the United States, 1976 to 1980. Paediatrics 8Z:l (1988).

10. Peckham C, Butler N: A national study of asthma in childhood. J Epidetniol Conim Health 32:79 (1978).

11. Lee DA, Winslow NR, Speight ANP, Hey EN: Prevalence and spectrum of asthma in childhood. Br Med J 286:1256 (1983).

12. Hill RA, Standen PJ, Tattersfield AE: Asthma, wheez- ing and school absence in primary schools. Arch Dis Child 64:246 (1989).

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

Fitzgerald JM, Sears MR, Roberts RS, Morris MM, Fester DA, Hargreave FE: Symptoms of asthma and airway hyperresponsiveness to methacholine in a population of Canadian schoolchildren. Am Rev Respir Dis 137:285 (1988). Peat JK, Woolcock AJ, Leeder SR, Blackburn CRB: Asthma and bronchitis in Sydney schoolchildren. Am ] Epideniiol 112:721 (1980). Mitchell C, Miles J: Lower respiratory tract symp- toms in Queensland schoolchildren. Aus t NZ J Med Z3:264 (1983). Crockett AJ, Ruffin RE, Schembri DA, Alpers JH: The prevalence rate of respiratory symptoms in school- children from two South Australian rural communi- ties. Azist NZ J Med 16:653 (1986). Jones DT, Sears MR, Holdaway MD, Hewitt C], Flannery EM, Herbison GP, et al: Childhood asthma in New Zealand. B r ] Dis Chest 83:332 (1987). Skarpaas IJK, Gulsvik A: Prevalence of bronchial asthma and respiratory symptoms in schoolchildren in Oslo. Allergy 40:295 (1985). Braback L, Kalvesten L, Sundstrom G: Prevalence of bronchial asthma among schoolchildren in a Swedish district. Acta Paediatr Scnnd 77821 (1988). Holmgren D, Aberg N, Lindberg U, Engstrom I: Childhood asthma in a rural country. Allergy 44:256 (1989). Williams H, McNicol KN: Prevalence, natural history and relationship of wheezy bronchitis and asthma in children. B r Med ] 4:321 (1969). Sibbald B, Horn MEC, Gregg I: A family study of the genetic basis of asthma and wheezy bronchitis. Arch Dis Child 5554 (1980). Redline S, Tishler PV, Lewitter FI, Tager IB, Munoz A, Speizer FE: Assessment of genetic and nongenetic influences on pulmonary function. A twin study. A m Rev Respir Dis 135:217 (1987). Ronchetti R, Lucarini N, Lucarelli P, Martinez F, Macri F, Carapella E, Bottini E: A genetic basis for heterogeneity of asthma syndrome in paediatric ages: adenosine deaminase phenotypes. ] Ailergy CIin lmrnunol74:81 (1984). Gortmaker SL, Walker DK, Jacobs FH, Ruch-Ross H: Parental smoking and the risk of childhood asthma. Am ]Public Health 72574 (1982). Kershaw CR: Passive smoking, potential atopy and asthma in the first five years. ] R Soc Med 80:683 (1987).

J A

sthm

a D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y U

B d

er L

MU

Mue

nche

n on

07/

04/1

4Fo

r pe

rson

al u

se o

nly.